Also see the margins, they usually would be adding 1+1 (left and right), so you have to make sure that report width + margins < interactive widthCheers,
Jason
P.S. : Please click the 'Mark as Answer' button if a post solves your problem! :)

Unfortunately I, like most users of the forum, aren't psychic; We'll need a bit more information on your problem before we can do more than guess at solutions. Can you describe what you're trying to do (i.e. your report) and what is happening. In this
particular case, details of the 'Size' propety of the body of your report and the 'Page Setup' from report properties yould be useful information to include. Also, do you have any items that span the whole width of the report?